15 April 2014

The infrared photo shows a temperature increase of only 9.8 degrees at the junction between the pantograph and the overhead charging rail of the Opbrid Bůsbaar at 625 A. Click to enlarge.

During recent tests of Hybricon Bus Systems’ new Arctic Whisper (HAW) urban bus in Umeå, Sweden (earlier post), the Opbrid Bůsbaar achieved ultrafast charging at 625 amps for 6 minutes. This paves the way for charging at 500 – 1000 kW or more to achieve 2- to 3-minute charges at the end stations of longer bus routes. It also allows all-electric heating and 5 – 6 minute charging for the upcoming 18 m 4WD Arctic Whisper articulated bus.

The Opbrid Bůsbaar is an overhead, pantograph-based fast-charging station for buses. In the future, this technology may enable other applications such as medium-distance electric buses or even long distance buses and trucks, the company said.

While fast charging of urban buses has already been shown to be a valuable way to achieve “infinite electric range” in bus systems by Hybricon, Proterra, Volvo, and others, bus operators want ever shorter charging times. If charging times can be reduced to just 2-3 minutes, then the operators do not have to add additional buses—and their associated costs—to a route.

The local bus operator only has a few minutes to charge at the ends of the route, so we developed this bus to satisfy this demand. We live close to the Arctic Circle and keeping passengers warm is also a top priority. Ultrafast Charging lets us heat with clean electricity instead of a diesel fuel burning heater.

—Jonas Hansson, CEO Hybricon Bus System

The tests recently completed consisted of charging the batteries of the Arctic Whisper at 625 Amps for 6 minutes. The infrared photo above shows a temperature increase of only 9.8 degrees at the critical junction between the pantograph and the overhead charging rail of the Opbrid Bůsbaar. The Opbrid Bůsbaar uses technology borrowed from the European electric rail industry which makes these results possible.

These tests validate our approach, which uses electric rail components such as Schunk pantographs and Furrer+Frey Conductor Rail. Besides transferring very high power, our Bůsbaar charging system is cost effective, safe and durable.

—Roger Bedell, CEO of Opbrid

The 12m Hybricon Arctic Whisper uses special batteries specifically designed for high charging rates and cold temperatures. The battery packs themselves are relatively small given the size of the vehicle—100 kWh in the case of the Arctic Whisper prototype. (The Arctic Whisper is configured as a series hybrid, with a 50 kW diesel backup system.) The BYD 12m (40-foot) battery-electric bus, for comparison, is equipped with a 324 kWh pack. In contrast, buses that require overnight charging must carry larger batteries. This gives the HAW more passenger capacity, more room inside the bus, and reduces weight and wear on roads.

Just a few chargers located at strategic points in Umeå can charge all of the Hybricon electric buses throughout the day. One hundred percent electric heating can also be used because there is plenty of energy available. The Umeå bus routes are relatively long and Ultrafast Charging provides sufficient power for continuous driving and heating on longer routes in this challenging climate.

The electricity in Umeå comes from renewable sources—primarily wind and hydroelectric dams. Converting the buses in Umeå from diesel to electricity using ultrafast charging saves both money and protects the environment. Hybricon Bus Systems will also be producing 4WD 18 meter electric buses for Umeå city starting this year.

HAW is the brand of the electric city buses developed and made by Hybricon Bus Systems in Umeå, Sweden. The HAW buses are modularly built and can be equipped with different battery types and pack sizes for different charging solutions. They can also be equipped with a range extender to widen the use of the buses, especially in the startup phase of electric bus fleets. However, its main focus is on Ultrafast Charging of a smaller battery pack for 24/7 electrical running in city traffic.

Comments

This is, I hope, the wave of the future. The ultra-fast charging will also drive demand for storage on the grid side to buffer the demand surges, and this storage will have a multitude of uses (regulation, spinning reserve, reactive power) beyond just charging.

Missings are what power source can generate these 625A at a decent voltage so 100KWH battery can be charged in 6mn. My guess is they need 1000 KW to perform that, hence 1600V at 625A - Waoooo ! I would love to see the size of the cables...
If they pull that from Green sources, I bet there is some serious energy storage put in between, and able to locally output that much energy when the bus arrives at the charging station. End to end cost of that energy including everything required here may not be that cheap, versus alternative Diesel...

I think people have hit the problems: you will need local storage to allow such a high charging current in smaller towns - it might be OK in a large city centre.

I would worry about the effect on battery life of such rapid charging, but I suppose they have that covered.

I wonder could they use diesel for heating in winter to reduce the electricity usage. Surely diesel (or kerosene or whatever) heaters can operate at very high efficiency - all they have to do is heat air. Thus, you could run a heater at 90-95% efficiency (a diesel engine would be <= 40%).
It depends on whether they are trying to use 0 hydrocarbons, or just run the system as efficiently as possible.

@harvey - a petrol pump can refuel at 22MW, this is talking about 0.5 - 1MW. If we assume a diesel bus is 45% the efficiency of an electric bus, it is still 10x faster - BUT, if they get this thing going, it will be a great piece of work.

Charging rate for this battery is the raison d'etre for choosing it: Lithium Titanate. Hybricon are using the using the Altairnano version. Proterra has been doing this for quite some time with the Toshiba version of LiT. (Remember Proterra? The evil, EVIL guys who probably threw the monkey wrench in the LTA purchase of BYD busses?) Proterra has been running demo/prototypes with their "FastFill" charger that goes up to aroung 400-500kW, if memory serves. 10C is not a problem.

The tradeoff is energy density. LiT isn't so great. However the strategy is to carry a much smaller battery and charge every time the bus completes a loop (maybe once an hour or two) for 5-10 minutes. BYD (clearly the much better and more ethical solution, or whatever, 'cause it's made in China) carries several tons of battery (literally) so it could be able to charge just once per day during a much longer break.

I can't find a reference, but I recall some discussion that a Vycon-styled flywheel storage solution (or the now defunct FreeBeacon) would be the buffer, if you will. IOW: charge the flywheel for 20 minutes at some power level of PkW, then charge the bus at 5xPkW for 5-10 minutes, repeating every half hour for a couple of busses. Admittedly a much bigger "system value" solution to the transportation organization choosing the bus.

In the meantime, there is hope for some readers as the Board of Directors for Altairnano (a key partner in Hybicon) consists mostly of Chinese nationals. But to dampen your enthusiasm their shares (ALTI on the Naz) have dropped in value by more than 50% since their peak last fall. Further we have still not seen an annual report for '13 yet, but we know sales and earnings(losses) for Q1-3 roughly add up to USD6M and (USD10M), respectively. Fortunately there are other LiT makers out there (Toshiba, Sony, YABO) who could take up the role.

Buses are particularly good candidates for ultra fast opportunity charging because they run the same route over and over. This is really a no-brainer.

What about long distance trucks and buses? Any hope there?

In the EU, long haul drivers have to stop for 45 minutes every 4.5 hours (this can be split into a 15 minute stop and 30 minute stop). In the US, it is now 30 minutes within an 8 hour period. Perhaps these rest stops could be used to add some grid power to long haul heavy vehicles?

Let's do some light math:
From a chart from VTT Finland, shows an energy output of the engine of a 60 ton tractor+trailer, full payload freeway at 80km/h is 168kW, including going up and down hills. Say an electric motor/battery is 90% efficient. We would consume about 190kW. As a sanity check, this corresponds to 190kW/h / 80 km/h = 2.4kWh per km, this seems about right for 60 tonnes.

So, in 4.5 hours, you would consume 855kWh out of the battery - rather a large battery!

To refill this in 45 minutes, you would have to charge at 1.2MW - a large amount, but not out of the realm of possibility, since this is only about 2C of that large battery.

The battery is just too big.

Does it make any sense to do this partially - using a plug-in hybrid? You will get some savings from reducing the hysteresis losses of going up and down hills, plus displacing diesel with as much power as you can charge during the stops.

Example:
300kWh of batteries
Gets you maybe 1.5 hours of runtime electric only, but the other 3 hours is on diesel. A reduction of about 40% in diesel usage if you add in the hysteresis reduction. To charge 300kW in 45 minutes, you only need a 400kW charger, well within current technology.

Not too bad, but not too wonderful either. Probably a non-starter until batteries get better, or diesel gets really expensive.

Delivery trucks, port trucks, trash trucks are likely a better business case, especially if a city has a zero emission or zero noise CBD, like is starting to occur in Europe.

Medium haul buses might be a good candidate, since they are much lighter than the above 60T truck, probably around 12T. In that case, a 300kWh battery might be sufficient.

Another alternative may be smaller quick charge batteries with an FC range extender. This type of hybrid could be scaled to fit small and large trucks and buses?

Aluminium + magnesium alloy 40-ft buses weight 4 to 5 tonnes less than the stainless steel version or about enough to fully offset the weight of the batteries and FC. A methane heater may be required for very cold places. A very high efficiency Heat Pump would do a good job in other places.

Siemens has demonstrated a pantograph system which can power trucks from overhead wires. The demonstration system was battery-less, switching to diesel power for passing. That would easily take care of long-distance driving, with batteries for the jaunts from the wired highways to endpoints.